The proposed research is designed to advance the understanding of the mechanisms of the absorption of ultrasound in biological material at the macromolecular level by studying the dependence of absorption and propagation speed upon (1) protein molecular size and conformation and (2) protein interactions in solution. The proposed approach is to (1) investigate parameters of interest by varying them in a controlled, systematic fashion obtaining absorption and propagation speed data under conditions where the molecular state of the biopolymer is known from other physical/chemical studies, and (2) examine the data in light of proposed absorption mechanism(s) and attempt to interpret the results as substantiation of one or more of these mechanisms. Specific experiments include: (1) measure several sugars of various molecular weights in the range 1 to 5 x 10 to the third power; (2) measure several globular proteins in molecular weight range 1 to 10 x 10 to the fourth power comparing (a) molecular weight differences, (b) differences due to alpha - helix content, and (c) monomeric vs. polymeric forms; (3) measure fibrous proteins in alpha-helix and random coil states; (4) measure fibrous proteins as a function of paracrystalline aggregation; (5) measure collagen in monodisperse, gel-like, and aligned fiber states; and (6) measure protein mixtures as a function of pH where isoelectric points of components are different. An understanding of the absorption behavior of biopolymers in solution is a necessary phase of the overall investigation of in vivo absorption mechanisms. The results of the proposed work will contribute to the knowledge of interaction mechanisms between sound and biological material and thus improve our ability to (1) understand and predict biological effects of ultrasound and (2) apply ultrasound clinically both as a diagnostic and as a therapeutic tool.